1. Field of the Invention
This invention relates to a novel method for determination of formaldehyde.
2. Description of the Prior Art
Since formaldehyde is produced as a reaction product during the course of several enzymatic reactions, the determination of formaldehyde has been carried out for assaying the enzymatic activities in said reactions or the substrate concentrations before the occurrence of enzymatic reactions.
For example, in the determination of triglycerides in plasma or tissues, the triglycerides are saponified to give glycerol, the glycerol formed is oxidized to give formaldehyde, the quantity of which is then determined; or in the determination of creatinine in serum or urine by an enzymatic method, the quantity of the creatinine is obtained by determination of formaldehyde resulting from the enzymatic reaction.
Formaldehyde is used as a raw material in the production of various resins. It is used also in improving the strength of textile fibers or improving the fiber strength in paper making. In addition, it is used as a fungicide or antiseptic. Further, it has been known that there are some of the daily necessaries such as tablewares, plywood furnitures and clothing articles which liberate a small amount of formaldehyde either in vapor state or as dissolved in water. The liberated formaldehyde is harmful to the human body, causing sometimes a poisoning which may lead to a rash.
For the above reasons, the determination of formaldehyde is important in the above-noted industrial fields as well as from the standpoint of hygienic chemistry.
For the determination of formaldehyde, there have heretofore been known several methods including, besides various colorimetric methods of determination, a method in which formaldehyde is allowed to react with an acetylacetone reagent in the presence of an ammonium salt and the resulting diacetyldihydrolutidine is fluorimetrically determined [S. Belman, Anal. Chim. Acta, Vol. 29, pp. 120-6 (1963)]. But, this method is unsuitable for the determination of an extremely small amount of formaldehyde because of the insufficient detection sensitivity due to the low fluorescence intensity of the formed fluorescent substance. The method has also a disadvantage in that the reaction between formaldehyde and acetylacetone is slow (requiring 5 hours at 20.degree. C.) and, when the reaction temperature is elevated for shortening the reaction time, the coloration of reaction mixture takes place, affecting adversely the accuracy of the determination.
The present inventors have previously been granted a patent for an improved method for determination of formaldehyde (U.S. Pat. No. 4,438,206) which comprises, in a method of formaldehyde determination by measuring the fluorescence of a fluorescent substance formed by allowing a formaldehyde-containing solution to react with an acetylacetone reagent, measuring the fluorescence in the presence of a serum albumin, particularly a bovine serum albumin.
Although this method has a high detection sensitivity and permits detecting an extremely small amount of formaldehyde with good sensitivity, it has not solved the problem of long reaction time and further has newly brought about an operational problem of requiring the addition of a substance other than the fluorescence reagent, namely a serum albumin.
Under the circumstances, the present inventors made an extensive study to find a more satisfactory method for determination of formaldehyde. As a result, it was found that the determination of formaldehyde can be performed with good accuracy and high speed when a compound represented by the general formula CH.sub.3 C(NH.sub.2).dbd.CHCO.sub.2 R, wherein R represents an alkyl group having 1 to 4 carbon atoms, is used as a fluorescence reagent capable of forming a fluorescent substance by the reaction with formaldehyde. Based on this finding, this invention has been accomplished.